Dispersion Behavior Of Particles Research Articles

Microgravity influenced unsteady dispersion during magnetic drug targeting in an inclined tumor-stenosed microvessel with slip effects

Introduction:Recent cancer research into microgravity or altered gravity environments has gained attention for its potential to disrupt cancer cell growth and proliferation while reducing the risk of chemoresistance—a major challenge in conventional chemotherapy. Aim of the study:Motivated by the emerging applications of microgravity in cancer research, the current study aimed to mathematically investigate the potential of the microgravity-enhanced environment in combination with magnetic drug targeting (MDT) to optimize drug delivery and dispersion. Methodology:The particle velocity, including microgravity’s influence in the presence of an external applied magnetic field alongside fluid pressure, was computed analytically while the solute dispersion model was numerically evaluated using the Crank–Nicolson method. Results:Findings show that microgravity lowers particle concentration in the tumor, however, improved drug-loaded magnetic nanoparticle properties, and magnetic field strength reveal a positive impact on nanoparticle accumulation. Also, altered stenosis height, inclination angle, slip velocity, and other control parameters such as Peclet number, magnetic-tumor distance, drug source term, elimination, and local skin friction revealed significant differences in particle dispersion behavior before, within, and after the stenosis region. Conclusion:Our results suggest potential future therapeutic applications of altered gravity in combination with MDT phenomena to improve drug delivery for noninvasive therapeutic strategies.

Application of shadowgraph imaging (SGI) particle characterisation data to interpret the impact of varying test conditions on powder dissolution and to develop an automated agglomeration identification method (AIM) in the USP flow-through apparatus

The aims of this work were 1) to explore the application of shadowgraph imaging (SGI) as a real time monitoring tool to characterize ibuprofen particle behaviour during dissolution testing under various conditions in the USP 4 flow-through apparatus and 2) to investigate the potential to develop an SGI-based automated agglomeration identification method (AIM) for real time agglomerate detection during dissolution testing. The effect of surfactant addition, changes in the drug mass and flow rate, the use of sieved and un-sieved powder fractions, and the use of different drug crystal habits were investigated. Videos at every sampling time point during dissolution were taken and analysed by SGI. The AIM was developed to characterize agglomerates based on two criteria – size and solidity. All detections were confirmed by manual video observation and a reference agglomerate data set. The method was validated under new dissolution conditions with un-sieved particles. Characterisation of particle dispersion behaviour by SGI enabled interpretation of the impact of dissolution test conditions. Higher numbers of early detections reflected greater dissolution rates with increased surfactant concentration, using sieved fraction or plate-shaped crystals, but was impacted by drug mass tested. An AIM was successfully developed and applied to detect agglomerates during dissolution, suggesting potential, with appropriate method development, for application in quality control.

Jet penetration and particle dispersion behaviors of supersonic gas–solid oxygen jet under high ambient temperature

Supersonic gas-powder mixing jets are widely utilized across various industrial processes such as fluidized bed, drug delivery, and steelmaking. In the current study, the impact of high-temperature environment on flow pattern and heat transfer behaviors of supersonic gas-powder flow in the convergent-divergent nozzle are numerically studied via Euler-Lagrangian method. Following validation through experiments, simulations are conducted across diverse conditions, involving four distinct ambient temperatures and powder feeding rates. The results reveal the following insights: (i) Increasing the ambient temperature from 500 K to 1000 K enhances the gas penetration depth and slows down the decay of particle velocity; (ii) The low-temperature gas within the jet core can obtain more energy from external environment via convection and thus expands more sufficiently; (iii) Once the powder mass flow rate surpasses a specific threshold of 8 kg/s, it fundamentally disrupts the supersonic flow structure and causes a large subsonic region downstream of the nozzle exit, substantially diminishing the capacity to accelerate particles; (iv) Increasing the particle feeding rate to 4 kg/s markedly amplifies particle radial dispersion; (v) Increasing the velocity difference between phases enhances both momentum and energy transfer. These findings offer significant insights into the behavior of supersonic gas-powder jets within high-temperature environments, contributing to the understanding of their dynamics and potential applications.

The dispersion and ignition behavior of zirconium particles under the effect of a shock wave

Experiments of the interaction process between shock waves and zirconium particles have been carried out using a self-designed shock tube. The interaction process was recorded using a high-speed shadowgraph imaging system, pressure testing system, and infrared thermal imager. The wave-systems structures resulting from the interaction between shock waves and accumulated zirconium powders have been characterized. Generally, the axial distance of the powder cloud reduces with the increase in accumulation thickness, which in turn increases with the addition of shock Mach number. The incident shock wave with an intensity of 1.53 Ma was enough to ignite zirconium powders under these experimental conditions. The ignition delay time for zirconium powders decreases with the addition of shock Mach number, while it decreases for thinner accumulations. Besides, the flame propagation characteristics and the ignition mechanism of zirconium powders are discussed in detail. The results can serve as a supplementary guide for the utilization and safe operation of zirconium powders.

Particle motion analysis of a new three-phase fluidized bed flotation column with glass sphere particles

Analysis of the particle movement within the unit vessel is necessary for the design, optimization and scale-up of the new three-phase fluidized bed flotation column (TFC). This work aimed to examine the motion and distribution of assisted fluidized particle-glass spheres in the TFC and to provide a better assessment of particle collision and dispersion behavior by quantifying particle velocities. Tracer particles were analyzed by high-speed camera techniques to determine particle velocity fluctuations in a three-phase fluidized bed consisting of glass spheres, water, and bubbles. A correlation model for determining the particle velocity in a three-phase fluidized bed is proposed after a systematic analysis of the particle velocity. The model covers a wide range of superficial gas velocities (0–0.339 m/s), superficial liquid velocities (0.169–0.425 m/s) and initial static bed heights (0.162–0.262 m). Aiming to evaluate particle collisions in the TFC, this paper derives the particle collision frequencies using a modified collision model and investigates the effect of a wide range of operating parameters on particle collisions. Finally, a new method for estimating dispersion due to particle motion is developed based on the study of particle dispersion coefficients.

Experiments and modelling of biomass pulverisation in swirling and non-swirling bluff body-stabilised turbulent annular flows

Deeper insights into particle loading have practical significance in applications particularly when this affects fuel-oxidiser mixing and flame stabilisation, as occurs in pulverised fuel (biomass) combustion systems. The underlying particle flow and dispersion characteristics not only play a crucial role in controlling overall combustion performance but can also impact emissions. A fundamental understanding of particle flow dynamics and dispersion behaviour for raw pulverised biomass, under non-swirling and swirling conditions need further systematic investigation to better understand the interplay between swirling and non-swirling bluff-body stabilised recirculation zones and particles emitted from a centralised jet. This work uses Particle Image Velocimetry (PIV) with three-dimensional multi-phase simulations based on the Discrete Phase Model (DPM) and Reynolds Stress Model (RSM) to investigate the flow and dispersion characteristics in confined flows typical of many practical combustors. Raw pulverised biomass-laden is introduced through a central turbulent jet (Rej = 4500 and 7800) and also subjected to turbulent annular flows (Res = 35,500), both non-swirling (S = 0) and swirling conditions (S = 0.3). Simulations are first validated against Constant Temperature Anemometry (CTA) resolved inlet boundary conditions and flow field PIV data under similar conditions.Results show that when a pulverised biomass-laden central jet interacts with a surrounding turbulent annular flow (non-swirling, swirling) the presence of a bluff-body based recirculating zone (BB-RZ) leads to biomass particle entrainment (pick up) and their recirculation over the bluff-body before being dispersed further downstream. Under non-swirling conditions, a significant 35% decrease in the mean particle axial velocity is measured coupled with an even more substantive 177% increase in turbulent fluctuation along the centreline. These findings are indicative of intense upstream (x/D ≈ 0.64) turbulent mixing and more intense particle dispersion into a BB-RZ. For swirling annular flow conditions near the end of the BB-RZ, the interaction between a biomass-laden central jet and the annular flow is comparatively weaker in the upstream region relative to non-swirling conditions. However, swirl significantly enhances downstream particle dispersion and lateral spread as reflected by a 254% hike in the mean particle radial velocity. Numerical predictions show that for the same particle loading ratio, but different (higher and lower) Reynolds number of a central particle-laden jet (i.e., the carrier gas), the conditions at relatively lower central jet Reynolds number allow better particle recirculation in BB-RZ as well as enhancing downstream lateral particle dispersion and entrainment, compared to a higher Reynolds number in the central jet. Outcomes from this investigation may have implications on the design and operation of pulverised (solid) fuel combustors if operated on renewably sourced biomass rather than traditional fossil fuels.

Numerical Simulation of the Particle Dispersion Behavior in Stirring Casting of Magnesium Matrix Composites

The dispersion behavior of SiC particles in molten Mg alloys during stirring casting using four-bladed stirrer was investigated by numerical simulation. The effects of stirring speeds (300, 500, 800 rpm) and stirring temperatures (590, 620, 640 °C) on the dispersion uniformity of the SiC particles were investigated. Simulation results show that the particle concentration fluctuates along both the height and radial directions of the stirred vessel to varying degrees. When the stirring casting was performed at 590 °C and at 300 rpm, a relatively uniform spatial distribution of SiC particles without large aggregations was obtained.

CFD modeling of particle dispersion behavior in the MIKE 3 apparatus

A simulation investigation on the flow domain and particle movement pattern in the dispersion stage of dust explosion experiment were conducted using CFD simulation based on Euler–Lagrange approach. A new solver that couples two phases was developed based on the default solver rhoPimpleFoam from the OpenFOAM tool kit. Three sizes of particles 25 μm, 125 μm and 250 μm were simulated and studied. The simulation results of dust front propagation were evaluated by the experiment data. Particles with smaller diameters tended to move slower. Due to the high turbulence, flow vortices in the lower part of the dispersion domain were identified. These vortices gradually became larger with time and the decrease of inflow velocity. Uneven distribution of particles along with the equipment and high concentration of particles between the discharge electrodes were found in the simulation. Furthermore, particles with higher velocity favored the middle position in the tube. These facts suggested that the ignition delay time for particles larger than 125 μm should be higher than 60 ms.

Effect of metal ions on the dispersion and agglomeration behavior of micro-fine wolframite

The effects of metal ion species, valence state, and pH on the dispersion and agglomeration behavior of micro-fine particles of wolframite were studied in this work. Adsorption capacity test, flotation kinetics, solution chemistry, zeta potential, and X-ray photoelectron spectroscopy (XPS) were used to evaluate the effect of metal ions on dispersion and agglomeration mechanism of micro-fine particles of wolframite. The results of turbidity and focused beam reflection measuring instrument tests showed that divalent and trivalent metal ions significantly affected the agglomeration behavior of micro-fine particles of wolframite compared with monovalent metal ions. Under specific pH conditions, divalent and trivalent metal ions destabilized and agglomerated the micro-fine particles of wolframite suspension. The results of XPS and solution chemistry showed that the Pb2+, Mn2+, Fe2+ and Al3+ adsorbed on the wolframite surface turned into hydroxide or hydroxyl complex, which improved the flotation rate of wolframite.

Study on dispersion behavior of submicron cerium oxide particles in concentrated suspensions by ultrasonic attenuation technique

Concentrated suspensions were prepared from submicron cerium oxide particles, and particle size distribution (PSD) and zeta potential of the particles were researched by ultrasonic attenuation technology and electroacoustic theory. The influences of particle concentration, base solution and pH value on particle dispersion behavior in suspensions were analyzed. It was found that for suspensions with concentration from 10 wt% to 30 wt%, the ceria particles were dispersed most sufficiently in the suspensions with sodium hexametaphosphate (SHP), while for suspensions with concentration 40 wt%, the particles were dispersed most sufficiently in the suspensions with deionized water (DIW) only. On the other hand, the particles agglomerated most remarkably in all suspensions with sodium carboxymethyl cellulose (CMC), and they had the lowest value of zeta potential. It was deduced that higher zeta potential could be helpful for particle dispersion in these concentrated suspensions, while non-DLVO interaction and dispersing process might play important roles too.

Improving particle dispersion characteristics with a novel cleaning screen: parameter design and numerical simulation

To reduce particle accumulation on a traditional planar-linear screen, a novel screen with sliding fingers and ladders was designed by numerical simulation and theoretical analysis. The dispersion behaviors of particles under the action of sliding finger and ladder were analyzed using the CFD-DEM (Computational Fluid Dynamics and Discrete Element Method). The effects of traditional and novel screens on the airflow distribution, particle motion and particle dispersion were investigated. The results indicated that the novel screen enhanced the airflow velocity and discharge in the traditional cleaning unit. This screen made the grains penetrate the sliding fingers, and the impurities were thrown behind the screen. It improved the particle accumulation on the traditional screen. The comprehensive dispersion degree of particles perpendicular to the entire novel screen surface was 8.14% higher than that with the traditional screen. The comprehensive dispersion degree of particles along the entire novel screen surface was higher by 6.87%.

Effect of impellers on particle mixing behaviour in KR desulphurization process

ABSTRACT Three types of impellers are developed to improve reagent efficiency in the desulfurization process of hot metal by kanbara reactor stirring method. The movement and dispersion behavior of particles are investigated using the CFD technology. The flow structure, particle volume fraction distribution and mixing time are taken as the characteristics to describe the entrainment ability and mixing ability of the impellers. The results show that the square center impeller (impeller B) improves the flow structure of the molten iron, and makes the volume fraction distribution of the particles much better than that of the traditional impeller (impeller A), the mixing time is the shortest among the three impellers under the same operating parameters. The blades with downward angle (impeller C and impeller D) improve the mixing effect of the region below the impeller, and the impeller C is more sensitive to the change of rotation speed.

Dispersion and agglomeration behaviors of submicron ceria particles in concentrated slurries

Dispersion and agglomeration behaviors of submicron ceria particles in concentrated slurries

Terminal Sequence-Specific Interparticle Attraction between DNA Duplex-Carrying Polystyrene Microparticles in Aqueous Salt Solution Assessed by Optical Tweezers.

The dispersion behavior of DNA duplex-carrying colloidal particles in aqueous high-salt solutions shows extraordinary selectivity against the duplex terminal sequence. We investigated the interparticle force between DNA duplex-carrying polystyrene (dsDNA-PS) microparticles in aqueous salt solutions and examined their behavior in relation to the duplex terminal sequences. Force-distance (F-D) curves for a pair of dsDNA-PS particles were recorded with a dual-beam optical tweezers system with the two optically trapped particles closely approaching each other. Interestingly, only 3-5% of the oligo-DNA strands on the dsDNA-PS particles formed a duplex with complementary DNAs, and the F-D curves showed a distinct specificity to the duplex terminal sequences in the interparticle force at a high-NaCl concentration; a clear attraction peak was observed in F-D curves only when the duplex terminal was a complementary base pair. The attractive strength reached 2.6 ± 0.5 pN at 500 mM NaCl and 4.3 ± 1.0 pN at 750 mM NaCl. By sharp contrast, no significant attraction occurred for the particles with mismatched duplex terminals even at 750 mM NaCl. Similar duplex terminal-specificity in the interparticle force was also confirmed for dsDNA-PS particles in divalent MgCl2 solutions. Considering that the duplex terminal sequences on the dsDNA-PS particles showed only a negligible difference in their surface charges under identical salt conditions, we concluded that the interparticle attraction observed only for the dsDNA-PS particles with complementary duplex terminals is attributable to the salt-facilitated stacking interaction between the paired terminal nucleobases (i.e., blunt-end stacking) on the dsDNA-PS surfaces. Our results thus demonstrate the occurrence of a duplex terminal-specific interparticle force between dsDNA-PS particles under high-salt conditions.

Estimation of dispersion coefficient in a solid-liquid fluidised bed system

Particle dispersion behaviour in a solid liquid fluidised system leads to interesting outcomes such as mixing and segregation which are often quantified by an empirical dispersion coefficient. The present study aims at providing a better estimation of particle dispersion behaviour from a fundamental definition analogous to diffusion coefficient. By tracking a tracer particle using high speed image analysis, fluctuating velocity components (Vi/) were determined in a solid-liquid fluidised bed comprising glass particles (dS = 8 mm, ρS = 2230 kg m−3) and water as a fluidising medium. Both inter-particle and particle-wall collisions were determined from the time varying jerk data. The particle mean-free path (λ) was then estimated as a distance between two successive peaks in the jerk profile. Finally, dispersion efficient D was computed based on the product of λ and V. Estimated dispersion coefficients were compared with the available correlations and reasonable agreement was obtained.

Aggregation characteristics of fine hematite and siderite particles in aqueous suspension

Siderite-bearing hematite is a type of refractory iron ore, where fine particle aggregation or dispersion behavior is of importance for the separation efficiency. Hence, the aggregation characteristics of fine particles (hematite and siderite) using sodium oleate (NaOl) as a flocculant were investigated through FBRM particle size analysis (a real-time particle characterization tool), zeta potential analysis, adsorption tests, contact angle measurements, and X-DLVO theoretical calculations. The results showed that NaOl could interact with hematite and siderite when the pH value ranged from 5.0 to 9.0, in which the hydrophobic interaction played a leading role in inducing homo-aggregation and hetero-aggregation in the mineral particles. However, in the strong alkaline solution environment (pH = 11.0), NaOl could only interact with siderite and scarcely adsorbed onto the hematite surface, which was mainly covered with ferric hydroxyl compound (Fe-OH). This largely prevented the formation of hematite-hematite and hematite-siderite aggregates in the suspension.

Development of a method for determining the maximum van der Waals force to analyze dispersion and aggregation of particles in a suspension

A new method for determining the maximum value of the van der Waals force, Fv,max, has been developed to analyze the dispersion and aggregation behavior of primary particles in a suspension. The simulation method considered the van der Waals force, the electrical double-layer force and the lubrication force as remote inter-primary-particle interaction forces. Distinct Element Method (DEM) was applied to tracking the motion of primary particles, and DEM was coupled with Computational Fluid Dynamics (CFD) by DEM-CFD coupling model to represent the motion in liquid. Aggregate size distributions (ASDs) were measured and simulated at different pHs and shear rates in order to determine the Fv,max and to validate the proposed method. The simulated ASDs qualitatively agreed with the experimental values in general. The result, therefore, indicates that the dispersion and aggregation behavior of primary particles could be analyzed by using the Fv,max determined by the proposed method.

Proper Orthogonal Decomposition Analysis and Dispersion Characteristics of Resonant Acoustic Flow

The investigation on the flow field and mixing characteristics of resonant sound mixing is of great significance for the dispersion mixing of superfine materials. In order to simulate the flow field and dispersion characteristics of resonant acoustic mixing, a gas-liquid-solid three-phase flow model based on the coupled level-set and volume-of-fluid (CLSVOF) and discrete particle model (DPM) was established. The CLSVOF model solves the gas-liquid interface, and the DPM model tracks the particle position. Then, the particle image velocimetry (PIV) experiment was performed using a self-made resonance acoustic hybrid prototype under different oscillation accelerations, and the radial velocity distribution between the experiment and simulation was compared. Finally, the proper orthogonal decomposition (POD) is used to decompose the flow field under different oscillation accelerations and fill levels, and the energy distribution law and the energy structure of different scales are extracted. The results show that the energy of the instantaneous flow field of the resonant sound is mainly concentrated in the low-order mode, and a close relationship was revealed between the energy distribution law and dispersion behavior of particles. The larger the small-scale coherent structures distribute, the more energy it has and the more favorable it is for fast and uniform dispersion.

Dispersion of praseodymium-doped zirconium silicate pigment in aqueous suspension by modified hydroxyl copolymer

Water-based copolymer dispersants, i.e., sodium polyacrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid-co-glycerol monomethacrylate (PASGS), were synthesized for dispersion of praseodymium-doped zirconium silicate pigment in aqueous suspension with polyacrylic acid-co-2-acrylamido-2-methylpropanesulfonic acid (PAS). Effects of different parameters on the dispersion behavior of colloidal particles were investigated via sedimentation tests. The samples were characterized by particle size analysis, Fourier transform infrared spectroscopy, and electrokinetic potential measurement. The interparticle potential energy at different pH values and dispersant types was calculated. The results show that PASG1 at 3wt.% addition effectively disperses the colloidal particles in the denser suspension of 35wt.% at pH 7.0, compared to PAS. Dispersant PASG1 provides greater steric hindrance and electrostatic repulsive energies than dispersant PAS. The dispersion/aggregation behavior of colloidal particles in the suspension under different conditions was also predicted by a modified population balance model (PBM). The predicted data are similar to the experimental results.

The Effect of pH and Salinity on the Rheological Properties of Drilling Mud Formulation from Natural Polymers

Drilling muds are designed to perform certain functions of drilling operation. Some of the functions are to cool and lubricate the drilling bit, transmit hydraulic power to drill bit, provide filter cake and remove drilling cuttings and maintaining wellbore stability. Various additives with specific properties are added in the mud to help prevent the challenges encountered during drilling process. The work studies the effect of pH and salt on the rheological properties of drilling mud formulation from two natural polymers (Terminaliamantaly(TM) exudate and Guar gum) with the use of Model 35 viscometer. Drilling mud formulation with these polymers was investigated at pH of (7.05, 8.15, 10.07, and 11.13) and salt concentrations of (2, 4, 6, 8 and 10g/ml). Results obtained from drilling mud with TM exudate were compared with drilling mud with guar gum. It was found thatthe rheological properties of drilling mud with Terminaliamantaly exudates increased for higher pH as compared to drilling mud with Guar gum. The increase in salinity reduced the effectiveness of the rheological properties of the mud such that as the salinity in drilling mud increased, the rheological properties of drilling mud with Terminaliamantaly and Guar gum decreased. The performance is attributed to flocculation, dispersion and hydration behavior of particles in the mud.